Digital out from CD ROM drive

[bifcake]

I was wondering if the audio out on the computer CD ROM drives that connects to the audio card is a digital out or an analog out? I looked at the connector and it's a 4 pin connector with left, ground, ground, right. That leads me to believe that it's an analog out. If that's the case, then I assume the only thing that a sound card does is act as an amplifier. Is that correct?

Additionally, if the out on the CD ROM drive is indeed an analog out, would it be possible to run the CD ROM drive simply as a transport? Where would I get the digital out? I'm trying to run an experiment of using a CD ROM drive as a transport and compare the performance against other CD transports using ML Model 30 DAC. I heard that Meridian uses CD ROM drives as CD transports within their players, so I was trying to see if I could build something like that on the cheap.

Thanks

PS. Please reply in layman's terms since my knowledge of electronics is very superficial.

 

[wasifazim]

Quote:

Originally posted by bifcake I was wondering if the audio out on the computer CD ROM drives that connects to the audio card is a digital out or an analog out? I looked at the connector and it's a 4 pin connector with left, ground, ground, right. That leads me to believe that it's an analog out. If that's the case, then I assume the only thing that a sound card does is act as an amplifier. Is that correct? Additionally, if the out on the CD ROM drive is indeed an analog out, would it be possible to run the CD ROM drive simply as a transport? Where would I get the digital out? I'm trying to run an experiment of using a CD ROM drive as a transport and compare the performance against other CD transports using ML Model 30 DAC. I heard that Meridian uses CD ROM drives as CD transports within their players, so I was trying to see if I could build something like that on the cheap. Thanks PS. Please reply in layman's terms since my knowledge of electronics is very superficial.

Most recent CD/DVD drives have a four pin analogue connector as well as a two-pin S/PDIF connector that hooks up to a sound card's internal S/PDIF socket. It's also possible to read digital audio through the IDE connection.

- Wasif.

 

[grinch]

i have been wondering this very same thing for a long time. the digital audio out port on a cd-rom is two pins. if you could make a cable that goes from the two-pin plastic jack to an rca jack, i'm pretty sure the dac would work. you may have to use a certain type of program to make the cd-rom play digitally and not analoguely (look ma, i invented a word!).

i know that my region-free dvd player uses a dvd-rom as the transport. it's easy to mod and change it to a faster one (if needed).

this is a very interesting idea and i hope you can get it to work.

 

[planar]

IMO, there is not much advantage on getting digital signal out of CD-ROM drive. CD-ROM drive reads audio track at 1x speed, not 40x or 50x or whatever-x speed that your CDROM has. Why? Audio CD has been developed earlier than CD-ROM for data, they only runs at 1x speed and there is no buffer or suspend storage area to re-organize the data (hence reduces the jitter). So what CD-ROM reads will be what you gets - it even includes mistakes.

So unless there is some kinds of re-clock chips on the way between CD-ROM and DAC board, the performance would actually be less than a typical CD-transport mechanism from Sony or philips. Because most of them now have some kind of re-clocking device, much or less.

Why, then, does Meridian uses CD-Rom?? Because it is easier to repair than a CD-transport mechanism. In fact, there is no need for repair, just change a new one. You know how cheap they cost these days.

So as long as the jitter is minimized between CD-ROM and DAC, you'll still get top performance all the way to the DAC.

There is another company in Australia which is selling CDP using CD-ROM as drive device. its called Redgum. Check their website for those informations.

SO, in conclusion, a bad CD-ROM transport will be:
CD-ROM -> DAC
A good one will be:
CD-ROM -> data buffering chip -> re-clocking device -> chip to seperate signal to left and right -> re-clocking again -> seperate DACs for Left and Right -> high quality analog out components.

That's why meridian charges you much more than a CD-Rom from Kmart.

 

[bifcake]

Planar,

That's very interesting. Especially considering that Meridian charges a gazillion dollars for their CD players.

What kind of a reclocking mechanism can you have between the CD transport and outboard DAC considering that the PCM stream has neither flow control nor parity checking?

 

[planar]

most manufactures use re-clock chip to re-clock the timing of digital signal. The re-clock chip has its own crystal-timing chips (master clock). The signal is re-clocked by the STANDARD of the timing of the RE-CLOCK chip, not the original reading data from cd-transport.

This will eventally introduce certain degree of jitter to the system. But it should be smaller than the oroginal jitter anyway.

I don't know whether there is a out-board re-clocking device available for home use. However, most of the outboard DACs contain re-clocking device already. So that shall decrease the jitter into a satisfying level.

 

[bifcake]

Are you saying then that attempting to build a CD rom drive as a transport with an outboard DAC is a worth while endeavor?

 

[planar]

Yes, but depends on the degree of hi-fi you want it to be. It could be either an easy task or a difficult one.

 

[bifcake]

I want to see if it would sound like $1000 or better transport. I want it to sound with a good DAC like an Adcom, Rega or a Musical Fidelity CD player. Naturally, I would use a good DAC, rather than a sound card. What do you think?

 

[Calanctus]

Some soundcards include SPDIF (digital) out, including Creative Audigy Platinum, M-Audio 2496 and others. This digital signal can be fed to an outboard DAC without any problem--I know, because I'm doing it now. (AFAIK all right/left outs are analogue.)

I haven't compared the sound quality to a good CD player, since mine needs to be fixed, but my brief listening so far says it's not bad.

 

[lini]

grinch: You'd need a little converter to do this, because CD/DVD-ROM-drives use a different sort of S/P-DIF-signal with TTL-output, whereas a normal S/P-DIF-output should have something like 0,75 V. I'm also not sure, whether the standard biphase mark coding is used for the TTL-version...

Greetings from Munich!

Manfred / lini

 

[MTRH]

Remove the analog & digi cable, use Winamp and install CD Reader.
voila, only your soundcard processes the audio, no extra stuff needed. very simple.

 

[bifcake]

MTRH,

That's not what I'm looking to do. I'm looking to use a CD Rom as a CD transport with an outboard hi-fidelity DAC. I want to see if this combo will sound better than a $1000 transport.

 

[Duncan]

Quote:

Originally posted by Calanctus Some soundcards include SPDIF (digital) out, including Creative Audigy Platinum, M-Audio 2496 and others. This digital signal can be fed to an outboard DAC without any problem--I know, because I'm doing it now. (AFAIK all right/left outs are analogue.) I haven't compared the sound quality to a good CD player, since mine needs to be fixed, but my brief listening so far says it's not bad.

Interesting, I was just about to post about this...

I personally think that my computer sounds superior to my CD Player... the CD Player setup, you can see in my 'signature' and my computer one is as such:

Philips 40x CD-Rom->SBLive!->Daughterboard->Cambridge Audio DAC->Meta42->Sony CD1700s

The sound quality using CDs I think is phenomenal, people here slate the SBLive quite a lot, but personally I don't see any bad issues with it (when run through my DAC at least), bass is punchy and fast, mids are smooth, and treble sparkling...

Whereas the Marantz, sounds a little bass shy, the mids sound hideously overblown in comparison to the PC, and the treble a shade subdued...

ALL setting on WMP and SNDCTRL32 on my PC are set to either flat, or off... so its as pure as its going to get...

The only complaint I have... without using error correction through WMP, CD Playback is dogged by pops, put on the correction and all is fine

Any thoughts as to why I think my PC is better than my Marantz?

Thanks

 

[MTRH]

keep in mind SBlive's resampling. Also are you sure windows eq i "0"? you should check that in the registry.